Fluorescent Tubes Generally
Fluorescent tubes were first designed and fabricated by Nikola Tesla, and presented at the Chicago World's Fair in 1893. These tubes were not made available to the consumer market however until mid-1938.
Fluorescent light is a light a light source achieved through the ionization of gases—a principle of operation known as cold plasma. A fluorescent lamp consists of a tube filled with a gas containing low pressure mercury vapor and argon (or some other ionziable gas), an electro-electronic circuit and two pairs of opposing terminals; the gas is ionized through the use of an electric current or an electromagnetic field.
Conventional fluorescent tubes have a higher efficacy than incandescent tubes, being that fluorescent tubes transform more of the electromagnetic energy into light than into heat. This is because the phosphorus deposited throughout the inner wall of the glass tube produces visible light when excited by the ultraviolet radiation generated by the ionization of the gas; there is no displacement of electrons through a solid medium such as a filament as is the case with incandescent lighting.
Fluorescent tubes are from two to four times more efficient and more economical (about 70%) than incandescent lamps (tubes). Although fluorescent tubes are superior to incandescent lamps in most respects, they are not without certain disadvantages.
Most fluorescent tubes contain toxic materials (ionizing gases, fluorescent pigments and mercury) which may be harmful to humans; therefore, a controlled and supervised disposal is required due to the risk of environmental contamination. Moreover, fluorescent tubes are typically designed to be installed in pairs. Thus, when one tube is defective and/or burned out, it is necessary to replace the both tubes, regardless of the other tube's condition.
Use of Light-Emitting Diodes for Lighting:
A light-emitting diode (LED) is an electronic component made from semiconductor materials that has the ability to generate light from electrical stimuli. Traditionally, light-emitting diodes were limited to use in electronic equipment, such as a visual signaler; this was due to the poor luminosity provided by early LED technology.
With the development of new technology and materials, it has become possible to fabricate high-power light-emitting diodes capable of providing light with an efficacy equal to or greater than that of the fluorescent tubes commonly used today. Furthermore, high-power light-emitting diodes are generally more efficient and economical than incandescent and fluorescent tubes. However, the use of said high-power light-emitting diodes in residential/industrial lighting poses a significant problem—with the extensive use of fluorescent lights, there was a significant investment in infrastructure (equipment technology) related to the installation of these tubes, after all, fluorescent tubes require adequate facilities (specific supports, specific reactors, specific connectors, among others) for their correct operation; thus, it is not economically viable to replace the entire infrastructure already existing with another type of technology.
In order to avoid this problem (not technical, but economic), adaptive designs were developed in order to allow the integration of light-emitting diodes (high-power or not) with existing infrastructure.
The current state of the art provides a multitude of adaptive designs, which LEDs are being used in fluorescent tubes. Examples of these designs are disclosed in the U.S. Pat. No. 6,583,550 and U.S. Pat. No. 7,114,830.
U.S. Pat. No. 6,583,550 filed in Oct. 23, 2001, discloses a fluorescent lamp composed of a glass tubular body internally coated with a fluorescent material. Inside of said fluorescent tube, there are light-emitting diodes (in this case, ultraviolet light). Its operating principle is similar to the one of a conventional fluorescent tube, i.e., the ultraviolet light causes the fluorescent material to produce visible light. It also discloses that the glass tubular body can be made of a ductile and translucent material, resulting in a flexible lamp with a capacity to change its shape. It must be noted that the efficacy of this lamp is still dependent on the quality and quantity of the fluorescent material used inside of the lamp and therefore becomes totally inoperative when the material is removed from the tube.
The U.S. Pat. No. 7,114,830 filed in Feb. 28, 2005, discloses a lamp consisting of a rigid transparent tube, a plurality of light-emitting diodes arranged within the tube, and a reflective coating disposed circumferentially about a portion of said tube. The emission of light from said light-emitting diodes is directed to the reflective coating of the tube. Although this lamp does not present the multitude of problems associated with traditional fluorescent tubes, its luminous efficacy is lacking because it does not support the use of high-power LEDs; being that this lamp is lacking an efficient means of heat dissipation, it must rely solely on conventional low-power LEDs
The lamps described in U.S. Pat. No. 6,583,550 and U.S. Pat. No. 7,114,830 are mere examples of the same concept. They disclose the adaptation of light-emitting diodes to conventional fluorescent tubes, allowing the lamps to be used with existing infrastructure (related to conventional fluorescent tubes). In these examples, as in many others, high-power light-emitting diodes are not used, which could increase the efficacy of the lamps.
High-power LEDs are also being used in certain lamps; in particular, lamps specially designed for integration with the conventional fluorescent tube infrastructure.
U.S. Patent Publication No. 2009-0261706 published on Oct. 22, 2009, discloses such a lamp. Said lamp comprises a plurality of high-power light-emitting diodes mounted to a printed circuit board, a heat sink and a translucent lens. The light-emitting diodes are mounted on the circuit board, by means of tin-lead solders, and the heat sink is fixed to this printed circuit board by means of heat paste. The heat sink is composed of an aluminum finned plate with a semi-circular profile.
On one hand, this design allows the fins to be in contact with the external environment, but on the other hand, it prevents an efficient heat exchange between the light-emitting diodes and the heat sink, respectively.
In addition, this lamp has an unnecessarily large inner dead space, which may have a detrimental effect on its heat dissipation and ultimately its efficacy. This problem is becoming more apparent as high-power light-emitting diode technology progresses. Since technological improvements have resulted in the creation of more powerful light-emitting diodes, LED lighting technology has become more dependent on efficient means of heat dissipation.
The present invention was developed based on the aforementioned concepts.